Certain actuators, hereinafter called orienting actuators, make it possible solely to orient the slats of a blind according to orientation commands supplied by a user through a remote control unit or according to information provided by a sensor. Other types of actuators, subsequently called movement actuators, allow only the upward and downward movement of the set of slats. Lastly, some actuators combine the two aforementioned functions.
The movement actuators have an output member driving a winder intended to rotate over several revolutions to drive the screen between a retracted position and a deployed position, either by winding and unwinding the screen itself, or by winding and unwinding one or several cords fixed to a load bar of the screen (the latter solution in particular being used for Venetian blinds). The number of revolutions between the deployed and retracted end-of-travel positions in particular depends on the distance between the end-of-travel positions and the diameter of the winder, but is generally counted in tens of revolutions. The winding and unwinding speed must be fast enough for the entire operation between the end-of-travel positions not to exceed several tens of seconds.
The orientation actuators have an output member driving a rocker rotating over at least one revolution, and which may include a front arm connected by a front cord to a front part of the slats, and a rear arm connected by a rear cord to a rear part of the slats. Significant precision is then desired over short travels.
The dimensions of the orientation and movement actuators are therefore radically different. However, industrial logic recommends using shared motors for these different actuators. Motors are then chosen with a relatively high rotation speed, which must be considerably reduced for the application to orientation actuators. This need creates a bulk issue that is difficult to reconcile with the size of the boxes used for the blinds.
For orientation blinds, one may also encounter a bulk issue independent of the bulk of the reduction gear associated with the motor. In particular, the available height of the box may vary based on the type of slats: in particular, the boxes for blinds with imitation wood slats are generally shorter than those for wood slats. Likewise, the spacing between the rockers may depend on the type of slats. Wood slats are in fact more rigid than imitation wood slats, and the spacing between the rockers as well as the distance available between the end of the box and the first rocker are thus generally smaller for blinds with slats made from imitation wood than for blinds with wood slats. As a result, the commercially available blinds with imitation wood slats generally do not have motors, the bulk for an actuator being greatly limited by the dimensions of the box and the locations of the rockers.
One solution used in the prior art is to offset the actuator part on the façade, as described in U.S. Pat. No. 5,444,339. This solution is not aesthetically satisfactory.
The alternative consists of using a specific low-speed motor, which is included in the bulk of the box. However, the development costs for such a motor, which is not standard relative to the full line proposed to motorize the different types of blinds or shutters, are high.